Nitrogen compounds Sandmeyer reaction

Reaction XLIX. (a) Action of Cuprous Potassium Cyanide on Aromatic Diazonium Compounds. (Sandmeyer). (B., 17, 1633, 2650 18, 1492, 1496.)—If a diazonium salt is added to a hot solution of cuprous-potassium cyanide, and the whole boiled on a water hath, nitrogen is evolved, and the corresponding nitrile formed. (C. r., 183, 421.)... 

For the preparation of chlorides or bromides, the diazonium salt is decomposed with a solution of cuprous chloride or bromide in the corresponding halogen acid (Sandmeyer reaction). It is possible to prepare the aryl bromide from the diazonium chloride or sulfate. A variation Involves the use of copper powder and a mineral acid for the decomposition step (Gattermann reaction). Both procedures are illustrated by the syntheses of the isomeric bromotoluenes and chlorotoluenes. The usual conditions of the Sandmeyer reaction fail in the preparation of the chloro- and bromo-phenanthrenes. However, these compounds can be successfully obtained by the interaction of the diazonium compound with mercuric and potassium halides (Schwechten procedure). Another procedure for formation of aryl bromides involves treatment of the amine hydrobromide with nitrogen trioxide in the presence of excess 40% hydro-bromic acid. The Intermediate diazonium perbromide is then decomposed by heat. ... 

For introduction of SCN into aromatic compounds the Sandmeyer reaction or its Gattermann variant is much more widely applicable than direct replacement of H by SCN (see page 202). An aqueous thiocyanate solution and CuSCN are added to a diazonium salt solution prepared in the usual way, or the addition is made gradually in the reverse direction — the diazonium salt to an aqueous solution of K3[Cu(SCN)4] copper powder can also be used.1264-1266 Reaction, with evolution of nitrogen, often occurs at room temperature or on... 

Perchlorination of triazines and related nitrogen compounds 346 Hoffmann degradation of perchloroaromatic amines 347 Other oxidations of 2,3,5,6-tetrachloro-p-phenylenediamine 348 An exceptional Sandmeyer-Schiemann-type reaction 350 Charge-transfer complexes 351... 

A -oxide which is easily reduced to codeine with sulphur dioxide [303]. The 0-methylation of certain Erythrina alkaloids has been carried out in a similar manner [304]. A -Oxidation has also been used to protect tertiary ring nitrogen atoms in heteroaromatic compounds. Protonation of the ring nitrogen atom in 4- (and 2-) aminopyridines renders their diazonium salts very susceptible to hydrolysis, thus they cannot be converted into cyanides by the Sandmeyer reaction. The corresponding TV-oxides may, however, be used in the normal way and the oxide function removed at a later stage, as in the sequence (63) (64) used by Berson and Cohen in studies on ipecac... 

Both the Sandmeyer and Meerwein reactions have been interpreted by heterolytic and homolytic mechanisms. Both reactions resemble halide replacements by involving solutions of complexes of Cu(I) with the reacting species, a diazonium compound. Cohen and Lewin have reported that a mixture of p-tolyldiazonium tetrafluoroborate and copper benzoate in aprotic solvents rapidly evolves nitrogen and forms toluene, bi(/)-tolyl), />-tolyl benzoate, and p,p-dimethylazobenzene (54). As was earlier suggested by Kochi 177), the azobenzene derivative is believed to arise from a reaction between an arylcopper species and the diazonium compound. A similar mechanism was suggested for the analogous reac-... 

---